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Date: Tue, 26 Jul 2005 23:56:24 -0700
From: Andrew Morton <akpm@osdl.org>
To: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: akihana@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: Reclaim space from unused ramdisk?
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Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
>
> >I wonder if it would be possible to somehow reclaim space that has
> >been previously reserved for a ramdisk without rebooting.
> 
> free_ramdisk.c:
> 
> #include <sys/ioctl.h>
> #include <sys/mount.h>
> #include <sys/stat.h>
> #include <sys/types.h>
> #include <errno.h>
> #include <fcntl.h>
> #include <stdio.h>
> #include <string.h>
> #include <unistd.h>
> 
> int main(int argc, const char **argv) {
>     int eax = 0;
>     while(*argv != NULL) {
>         int fd = open(*argv, O_RDWR);
>         if(fd < 0) {
>             fprintf(stderr, "Warning: Cannot open %s: %s\n",
>              *argv, strerror(errno));
>             if(eax == 0) { eax = errno; }
>             continue;
>         }
>         ioctl(fd, BLKFLSBUF, 0);
>         close(fd);
>         ++argv;
>     }
>     return eax == 0;
> }
> 

hmm, yes.  That's a special-case in the ramdisk driver.

The command `blockdev --flushbufs /dev/ram0' should have the same effect.